The British pound's rapid fall to 11-year lows against European currencies has pushed the UK into sixth place in the world's economy.
The US, Japan, Germany, China and France had the largest economies in the third quarter of 2007, according to the Financial Times.
Sterling dropped to its weakest against the euro, which in turn, resulted in Britain's economy slipping below France for the first time since the single currency was introduced in 1999.
The UK economy is now four percent smaller than its ancient rival France and it is expected that the pound will weaken as interest rates fall and the British economy slows.
Britain was the fourth largest economy in the world until 2005 when China took its place.